The present invention relates to alignment of semiconductor wafers and other articles.
Fabrication of integrated circuits from a semiconductor wafer involves many processing steps, and the wafer may have to be aligned as it goes from one step to the next. For example, before a wafer is diced, it has to be attached to an adhesive film stretched over a frame, which requires accurate alignment of the wafer to the frame. Alignment is performed using a piece of equipment called aligner. A robot picks up the wafer and places it on the aligner. The aligner adjusts the position of the wafer in the horizontal plane to cause the center of the wafer to occupy a predetermined position. Then the aligner rotates the wafer to place the wafer into some predetermined rotational orientation, i.e. with some feature (a notch or a flat) on the wafer's circumference in a predetermined position. Then the robot picks up the wafer again and carries the wafer to a target station for the next processing step.